The present invention generally relates to X-ray tubes and, more particularly, is concerned with an X-ray tube assembly.
Medical X-ray devices, including those employed in computed tomography, generally contain an X-ray tube. An X-ray tube typically includes a cathode, an anode and a stationary frame surrounding the cathode and anode. The cathode is stationary while the anode rotates relative to the cathode. The surrounding frame contains a vacuum chamber and has an X-ray transparent window. The anode has a target surface which faces the cathode. The cathode emits electrons which strike the target surface of the anode and produce X-rays. Some of the X-rays exit the frame as an X-ray beam through the X-ray transparent window.
Load-carrying bearings are located inside the vacuum chamber between the frame and a stem of the anode. The bearings must be lubricated. The target surface of the anode is heated by the impinging electrons. The heat of the target surface is dissipated by thermal radiation and conduction to the frame. The heated frame is cooled by a liquid coolant, such as oil or water, located between the frame and a surrounding casing.
Thermal management requirements have caused the mass and the speed of rotation of the anode to increase dramatically in recent years which adversely affects the performance of bearings over time. Current X-ray tube designs are close to the limits of X-ray tube bearing technology and to the limits of technology available for thermal management.
Consequently, a need exists for an X-ray tube design which will avoid the problems associated with current X-ray tube designs in terms of bearing technology and thermal management without introducing any new problems in place thereof.